/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *          http://www.apache.org/licenses/LICENSE-2.0
 *
 *   Unless required by applicable law or agreed to in writing, software
 *   distributed under the License is distributed on an "AS IS" BASIS,
 *   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *   See the License for the specific language governing permissions and
 *   limitations under the License.
 */

package com.jthemedetecor.util;

import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;

public class ConcurrentHashSet<E> implements Set<E> {

    private final Map<E, Object> map;

    private static final Object OBJ = new Object();

    public ConcurrentHashSet() {
        map = new ConcurrentHashMap<>();
    }

    @Override
    public int size() {
        return map.size();
    }

    @Override
    public boolean isEmpty() {
        return map.isEmpty();
    }

    @Override
    public boolean contains(Object o) {
        return map.containsKey(o);
    }

    @Override
    public Iterator<E> iterator() {
        return map.keySet().iterator();
    }

    @Override
    public Object[] toArray() {
        return map.keySet().toArray();
    }

    @Override
    public <T> T[] toArray(T[] a) {
        return map.keySet().toArray(a);
    }

    @Override
    public boolean add(E e) {
        return map.put(e, OBJ) == null;
    }

    @Override
    public boolean remove(Object o) {
        return map.remove(o) != null;
    }

    @Override
    public boolean containsAll(Collection<?> c) {
        return map.keySet().containsAll(c);
    }

    @Override
    public boolean addAll(Collection<? extends E> c) {
        boolean changed = false;
        for (E e: c) {
            if (map.put(e, OBJ) == null) {
                changed = true;
            }
        }
        return changed;
    }

    @Override
    public boolean retainAll(Collection<?> c) {
        throw new UnsupportedOperationException();
    }

    @Override
    public boolean removeAll(Collection<?> c) {
        throw new UnsupportedOperationException();
    }

    @Override
    public void clear() {
        map.clear();
    }
}